Led lamp with infrared output

Abstract

An light emitting device, may include pump LEDs or lasers and one or more phosphors allowing the lamp to emit light with a spectral power distribution having a local minimum at a water vapor absorption band, such as at 950-990 nm. Such a device may be used in radiotherapy based on hyperthermia, providing light that penetrates tissue without risk of skin overheating. Utilizing LEDs or lasers may allow the light emitting device to achieve higher efficiency, better form factor, and lower operating temperatures than water-filtered halogen lamps utilized in radiotherapy.

What is claimed is: 
     
         1 . A light emitting device comprising:
 a plurality of light emitters comprising light emitting diodes or lasers that emit a first light having a first peak wavelength;   a phosphor layer arranged in an optical path of the light emitters, the phosphor layer comprising two or more phosphors arranged to absorb the first light and emit a second light, the second light having a spectral distribution (SPD) comprising a first local maximum wavelength, a second local maximum wavelength, and a first local minimum wavelength at 950-990 nm and between the first and second local maximum wavelengths.   
     
     
         2 . The light emitting device of  claim 1 , wherein the two or more phosphors comprise a first phosphor arranged to absorb the first light and emit a third light having a second peak wavelength that is the first local maximum wavelength, and a second phosphor arranged to absorb the first light and emit a fourth light having a third peak wavelength that is the second local maximum wavelength, such that the second light comprise the third light and a fourth light. 
     
     
         3 . The light emitting device of  claim 1  wherein the first local maximum wavelength is greater than the second local maximum wavelength, and a first power of the third light at the second peak wavelength is greater than a second power of the fourth light at the third peak wavelength. 
     
     
         4 . The light emitting device of  claim 3 , wherein the phosphor layer is arranged to transmit a remaining first light after absorbing some of the first light, the remaining first light having a third power at the first peak wavelength less than the first power, the third power being equal to 0-2% of the total spectral power of light emitted by the light emitting device. 
     
     
         5 . The light emitting device of  claim 3 , wherein the third power is less than the second power. 
     
     
         6 . The light emitting device of  claim 2 , wherein the first local maximum wavelength is in the range of 1000-1100 nm, and the second local maximum wavelength is in the range of 700-900 nm. 
     
     
         7 . The light emitting device of  claim 2 , wherein the phosphor layer comprises a third phosphor having a fourth peak wavelength different from the second and third peak wavelengths. 
     
     
         8 . The light emitting device of  claim 1 , wherein the phosphor layer comprises resin encapsulating the two or more phosphors. 
     
     
         9 . The light emitting device of  claim 1 , wherein the two or more phosphor comprises a first phosphor comprising chromium. 
     
     
         10 . The light emitting device of  claim 1 , wherein the two or more phosphor comprises a second phosphor comprising chromium. 
     
     
         11 . The light emitting device of  claim 10 , wherein the second phosphor comprises ytterbium. 
     
     
         12 . The light emitting device of  claim 10 , wherein the first phosphor crystallizes in a pyroxene structure type and the second phosphor crystallizes in a garnet structure type. 
     
     
         13 . The light emitting device of  claim 10 , further comprising a second phosphor layer arranged in an optical path of the light emitters, the second phosphor layer arranged to absorb the first light and emit a third light having a second peak wavelength in the visible range. 
     
     
         14 . The light emitting device of  claim 13 , wherein the second peak wavelength is in a range of 620-750 nm. 
     
     
         15 . The light emitting device of  claim 1 , wherein the light emitters comprise light emitting diodes. 
     
     
         16 . The light emitting device of  claim 1 , wherein the light emitters comprise lasers. 
     
     
         17 . The light emitting device of  claim 1 , wherein the first light has the first peak wavelength is in the range of 450-495 nm. 
     
     
         18 . The light emitting device of  claim 1 , wherein a first power spectral ratio of a first wavelength interval of 950-990 nm over a second wavelength interval of 860-900 nm is less than or equal to 80%. 
     
     
         19 . The light emitting device of  claim 1 , wherein a second power spectral ratio of a first wavelength interval of 950-990 nm over a second wavelength interval of 1020-1060 nm is less than or equal to 90%. 
     
     
         20 . The light emitting device of  claim 1 , further comprising a collimator arranged in an optical path of the light emitters and the phosphor layer and arranged to collimate the first and second light.